It's possible to target an activity to any URL using the criteria shown in the screenshot. As you can see the hash character should not bring any issue. Yes, I tried to add a hash character in the middle.
If the page can't be opened in the browser directly, this is likely how the SPA works. If it can be opened in the browser, but is not loaded in the VEC, then maybe this is because of the http headers (see the Mihnea's reply)j, or with the library, or unsafe scripts, or something else.
If the extension does not make the VEC work for the app, check whether the Enhanced Experience Composer (EEC) is disabled (Setup > Preferences). Toggle the control and try again.
I think it's important to understand that Target could and can be used with any SPA in general. As I understand, the key objective of V2 is to enable VEC for SPA. But if you want to go ahead with the form composer or server-side implementation, then V2 is just one of the options.
P.S.: Consider to involve your account manager or CSM to the scenario you are working on.